Self-aligned passivation of active regions

Abstract

A method includes forming a semiconductor fin, performing a first passivation step on a top surface of the semiconductor fin using a first passivation species, and performing a second passivation step on sidewalls of the semiconductor fin using a second passivation species different from the first passivation species. A gate stack is formed on a middle portion of the semiconductor fin. A source or a drain region is formed on a side of the gate stack, wherein the source or drain region and the gate stack form a Fin Field-Effect Transistor (FinFET).

What is claimed is: 
     
       1. A method comprising:
 recessing isolation regions on opposite sides of a semiconductor region, wherein a top portion of the semiconductor region higher than top surfaces of the isolation regions forms a semiconductor fin; 
 performing a first passivation step on a top surface of the semiconductor fin using a first passivation species; 
 performing a second passivation step on sidewalls of the semiconductor fin using a second passivation species different from the first passivation species, wherein the first passivation step and the second passivation step are performed after the step of recessing the isolation regions, wherein the first passivation step and the second passivation step are performed simultaneously; and 
 forming a gate stack on the semiconductor fin. 
 
     
     
       2. The method of  claim 1 , wherein the semiconductor fin comprises germanium. 
     
     
       3. The method of  claim 1  further comprising:
 forming a dummy gate stack to cover a middle portion of the semiconductor fin; 
 forming an Inter-Layer Dielectric (ILD) to cover end portions of the semiconductor fin; and 
 removing the dummy gate stack to expose the middle portion of the semiconductor fin, wherein at least one of the first passivation step and the second passivation step is performed after the step of removing the dummy gate stack. 
 
     
     
       4. The method of  claim 1  further comprising:
 forming a dummy gate stack to cover a middle portion of the semiconductor fin; 
 forming an Inter-Layer Dielectric (ILD) to cover end portions of the semiconductor fin; and 
 forming contact openings in the ILD to expose the end portions of the semiconductor fin, wherein at least one of the first passivation step and the second passivation step is performed after the step of forming the contact openings. 
 
     
     
       5. The method of  claim 1 , wherein in the first passivation step, dangling bonds at the top surface of the semiconductor fin are connected to atoms of the first passivation species. 
     
     
       6. The method of  claim 1 , wherein the first passivation species are selected from the group consisting essentially of sulfur, selenium, and combinations thereof, or the second passivation species are selected from the group consisting essentially of antimony, sulfur, arsenic, and combinations thereof. 
     
     
       7. A method comprising:
 performing a first passivation step on a top surface of a semiconductor region using a first passivation species, wherein the semiconductor region is between isolation regions, with the top surface of the semiconductor region being substantially level with top surfaces of the isolation regions; 
 after the first passivation step, recessing the isolation regions, wherein a top portion of the semiconductor region higher than top surfaces of remaining portions of the isolation regions forms a semiconductor fin; 
 after the step of recessing, performing a second passivation step on the semiconductor fin using a second passivation species different from the first passivation species, wherein the first passivation step is performed using the first passivation species selected from the group consisting essentially of sulfur, selenium, and combinations thereof, or the second passivation step is performed using the second passivation species selected from the group consisting essentially of antimony, sulfur, arsenic, and combinations thereof; and 
 forming a gate stack on the semiconductor fin. 
 
     
     
       8. The method of  claim 7 , wherein the first passivation step is performed using the first passivation species selected from the group consisting essentially of sulfur, selenium, and combinations thereof. 
     
     
       9. The method of  claim 7 , wherein the second passivation step is performed using the second passivation species selected from the group consisting essentially of antimony, sulfur, arsenic, and combinations thereof. 
     
     
       10. The method of  claim 9 , wherein the second passivation species further comprises a second species selected from the group consisting essentially of chlorine, arsenic, and combinations thereof. 
     
     
       11. The method of  claim 7  further comprising:
 forming a dummy gate stack to cover a middle portion of the semiconductor fin; 
 forming an Inter-Layer Dielectric (ILD) to cover end portions of the semiconductor fin; and 
 removing the dummy gate stack to expose the middle portion of the semiconductor fin, wherein the second passivation step is performed after the step of removing the dummy gate stack. 
 
     
     
       12. The method of  claim 7  further comprising:
 forming a dummy gate stack to cover a middle portion of the semiconductor fin; 
 forming an Inter-Layer Dielectric (ILD) to cover end portions of the semiconductor fin; and 
 forming contact openings in the ILD to expose the end portions of the semiconductor fin, wherein the second passivation step is performed after the step of forming the contact openings. 
 
     
     
       13. A method comprising:
 forming a semiconductor fin; 
 performing a first passivation step on a top surface and sidewalls of the semiconductor fin using a first passivation species, wherein the first passivation species comprises a first element and a second element, wherein the first element is selected from the group consisting essentially of sulfur, selenium, and combinations thereof, and the second element is selected from the group consisting essentially of antimony, sulfur, arsenic, and combinations thereof; and 
 forming a gate stack on the semiconductor fin. 
 
     
     
       14. The method of  claim 13 , wherein the first passivation species further comprises a third element. 
     
     
       15. The method of  claim 14 , wherein the third element is selected from the group consisting essentially of chlorine, arsenic, and combinations thereof. 
     
     
       16. The method of  claim 13 , wherein the first passivation step comprises a method selected from the group consisting essentially of an implantation of the first passivation species, a plasma generation of the first passivation species, a gas phase of the first passivation species, and a liquid phase of the first passivation species. 
     
     
       17. The method of  claim 16 , wherein the first passivation step comprises the implantation, and wherein the method further comprises annealing the semiconductor fin after the implantation. 
     
     
       18. The method of  claim 16  further comprising:
 forming a dummy gate stack to cover a middle portion of the semiconductor fin; 
 forming an Inter-Layer Dielectric (ILD) to cover end portions of the semiconductor fin; and 
 performing a second passivation step on the exposed middle portion of the semiconductor fin. 
 
     
     
       19. The method of  claim 16 , wherein the first passivation step comprises a gas phase of the first passivation species. 
     
     
       20. The method of  claim 16 , wherein the first passivation step comprises a liquid phase of the first passivation species.